I've always bought them online. I got the ones for my 40 actually from Toyota (I know that doesn't help you). I was really happy with the ones I got for my bus back then. The vendors pretty much all sell the same stuff, and due to DOT regs it's going to be at least as good as a modern Chrysler product. I got a set with the aircraft style buckle like what was in my dad's Mustang when I was a kid.

I have a sack full of FJ60 seatbelts and parts if you want to dig through it.

__________________
Tim M Hovey
1950 cj3a: FJ60 Axles, brakes, and steering, Willy's
sheetmetal and a Buick engine, held together with
metal from the scrap yard glued together in a garage in
Louisville and dragged around behind a F350 Diesel.